Effects of pasture species and irrigation on milk production over four summers in the Waikato

Milk production by Jersey cows grazing a common allowance of irrigated or non-irrigated pastures over four summers (1997-2000) is described. The pastures were: (1) high-endophyte perennial ryegrass-white clover (2) tall fescue, phalaris, cocksfoot, white clover, red clover (3) same as (2) plus paspalum (4) endophyte-free ryegrass, timothy, white clover, red clover and (5) existing high-endophyte ryegrass-white clover. Irrigation improved milksolids yield by 5% over 4 years, with inconsistent effects on milk composition, no effects on pasture in vitro digestibility and nitrogen content, and usually no effect on pasture botanical composition. In 1997, cows on (1) produced the lowest milksolid (MS) yields. Cows grazing ryegrass-white clover (1 and 5) produced less than those on tall fescue-based pastures (2 and 3) (0.74 vs 0.86 kg MS/cow/day) in 1998, and the yields of cows on ryegrass/timothy-based pastures (4) were best (0.96 kg MS/cow/day). The same trends in milksolids yield occurred in 1999, except for cows on (1) which were similar to (4). Cows on existing pasture often produced the lowest milksolid yields. Trends in milksolids production over the 4 years reflected trends in total clover (red + white) contents. Keywords: cocksfoot, dairy cows, grazing, pasture quality, perennial ryegrass, persistence, phalaris, red clover, tall fescue, timothy, triple mix, volunteer ryegrass, white clover